Field of the Invention
The present invention relates to an end seal structure of a fuel rail (delivery pipe) for supplying a high-pressure fuel, which is supplied from a fuel booster pump of an electronic fuel injection-type automobile engine or the like, through a fuel injector (an injection nozzle) for directly injecting the fuel into an engine cylinder. More specifically, the present invention relates to an end seal structure of a fuel rail for a gasoline direct injection engine structured to directly supply the fuel from the rail to the injector with an injection pressure on the order of 20 to 100 MPa.
Description of the Related Art
Some exemplary fuel rails can be mentioned as conventional fuel rails for gasoline direct injection engines of this type. For example, an exemplary fuel rail includes a main pipe and a plurality of branch pipes and is structured such that through-holes for receiving each branch pipe are formed in an outer wall of the main pipe, each through-hole having an annular wall that projects toward the outside and inside of the main pipe, respectively, and each branch pipe being fixed to the annular wall. Another exemplary fuel rail is structured such that a branch pipe is connected to a body, which is an accumulating vessel, directly or via a branch joint fitting (nipple). Yet another exemplary fuel rail is structured such that a socket for connection of an injector is directly attached to a rail body composed of a tubular member such as a pipe.
Further, other exemplary fuel rails may be mentioned as the fuel rail structured such that the socket for connection of the injector is directly attached to the rail body composed of a tubular member such as a pipe. For example, an exemplary fuel rail includes an injector holder and a fastening bracket that are directly attached to a rail body composed of a tubular member such as a pipe into which pressurized fuel is supplied from a high-pressure fuel pump (see Japanese Patent Laid-Open No. 2010-7651). Also, a high-pressure fuel delivery pipe for a direct injection engine includes a cylindrical body pipe into which pressurized fuel is supplied from a high-pressure fuel pump, a plurality of sockets to which fuel injection valves coupled to the body pipe and operable to be opened and closed by a control unit are coupled, and a plurality of mounting stays integrally fastened to the body pipe so as to attach the body pipe to the engine (see Japanese Patent Laid-Open No. 2011-144768).
However, the above-mentioned conventional fuel rails for gasoline direct injection engines have the following problems.
That is, in the above-mentioned various conventional fuel rails for gasoline direct injection engines, a rail body composed of a tubular member such as a pipe is structured such that one end or both ends thereof are closed, and its end rail structure is, for example, as illustrated in FIGS. 2 and 3 as enlarged views, generally structured such that end caps 112A and 112B are joined by brazing to corresponding one of the ends of the openings of a cylindrical body pipe 111.
Meanwhile, a problem that is identified and should be addressed is the strength of the end caps 112A and 112B closing the both ends of the body pipe 111 in the trends of higher pressures in gasoline direct injection systems. Specifically, the following and other problems are identified. In the case of the end seal structure structured by joining the end caps 112A and 112B by brazing to the body pipe 111 as illustrated in FIGS. 2 and 3, the end seal structure is structured such that, when an internal pressure is applied in the body pipe 111 which is the rail body, a force generated when the body pipe 111 is deformed in the radial direction (swelling toward the outside of the tubular member) is received by brazed parts 113A and 113B, respectively, so that these brazed parts 113A and 113B become the weakest parts in terms of their strength. This makes it difficult for gasoline direct injection systems to meet their higher-pressure requirements.
Further, since the brazed parts 113A and 113B are in direct contact with the fuel (pressure medium), if there is any unevenness in the shape of these brazed parts, then it tends to become a factor of breakage of the brazed parts due to the concentration of stress.